Last week, I discussed new research linking even relatively modest levels of regular physical activity with a reduced risk of developing breast cancer (Even Modest Levels of Physical Activity Decrease Breast Cancer Risk). This week, I will present a newly published clinical research study that may help to explain the well known links between obesity, weight loss, and breast cancer risk. This new research study appears in the current issue of theJournal of Clinical Oncology.

There is ample evidence that obesity is, by itself, a risk factor for breast cancer, and that the loss of excess weight can reduce obesity-associated breast cancer risk. Similarly, a womans lifetime level of exposure to the female sex hormone estrogen (as well as to testosterone) has also been linked to breast cancer risk.

After menopause, the ovaries no longer produce estrogen. However, fat cells continue to produce estrogen (and to metabolize testosterone into estrogen), and the link between obesity and breast cancer has, therefore, been presumed to be due to increased estrogen production from fat cells in the bodies of overweight and obese women. Based upon the findings of this new clinical study, the presumed biological mechanism whereby loss of excess weight reduces breast cancer risk appears to have been confirmed.

In this prospective, randomized, controlled clinical study, obese, sedentary postmenopausal women (ages 50 to 75 years) were randomized into one of four different groups. The first group was placed on a reduced calorie diet. The second group engaged in a supervised moderate-to-vigorous aerobic exercise program. The third group underwent both dieting and a supervised exercise program. Finally, the fourth group of women served as a control group, and these women did not engage in either dieting or exercise. Blood levels of estrogen and testosterone were measured in all of these women at the beginning and end of this 12-month study.

Compared with the women in the control group, estrogen levels decreased by 16 percent with dieting alone, by 5 percent with exercise alone, and by more than 20 percent when dieting was combined with moderate-to-vigorous exercise. Similarly, testosterone levels declined by 10 percent with dieting alone, and by almost 16 percent when dieting was combined with exercise. Moreover, greater levels of weight loss were associated with greater decreases in estrogen and testosterone levels.

The findings of this innovative clinical research study lend considerable weight to the longstanding theory that obesity increases breast cancer risk by raising estrogen and testosterone levels in postmenopausal women, while the loss of excess weight decreases breast cancer risk due to reductions in obesity-related elevated levels of estrogen and testosterone. While there are, doubtless, other biological mechanisms involved, this clinical study adds considerable weight to the data that I discuss in my bestselling book,A Cancer Prevention Guide for the Human Race, linking diet, obesity and exercise (along with other modifiable lifestyle factors) to breast cancer risk.

As our society becomes progressively more obese and sedentary, the incidence of cancer and other serious obesity-related diseases is expected to continue to climb. If you are significantly overweight, or if you lead a couch potato lifestyle, then please meet with your doctor and a personal trainer, and get started on a sensible diet program (as I describe in my book) and exercise program.

At this time, more than 8 percent of Americans are unemployed. According to the Bureau of Labor Statistics, however, the unemployment rate for veterans who served on active duty between September 2001 andDecember 2011 is now more than 12 percent. A new website,Veterans in Healthcare,seeks to connect veterans with potential employers. If you are a veteran who works in the healthcare field, or if you are an employer who is looking for physicians, advanced practice professionals, nurses, corpsmen/medics, or other healthcare professionals, then please take a look atVeterans in Healthcare.As a retired veteran of the U.S. Army, I urge you to hire a veteran whenever possible.

For a groundbreaking overview of cancer risks, and evidence-based strategies to reduce your risk of developing cancer, order your copy of my bestselling book, A Cancer Prevention Guide for the Human Race, fromAmazon,Barnes & Noble,Books-A-Million,Vromans Bookstore, and other fine bookstores!

Within one week of publication,A Cancer Prevention Guide for the Human Race was ranked #6 among all cancer-related books on theAmazon.com “Top 100 Bestseller’s List” for Kindle e-books. Within three months of publication, A Cancer Prevention Guide for the Human Race was the #1 book on theAmazon.com “Top 100 New Book Releases in Cancer” list.

Disclaimer: As always, my advice to readers is to seek the advice of your physician before making any significant changes in medications, diet, or level of physical activity

Dr.Wascher is an oncologic surgeon, professor of surgery, cancer researcher, oncology consultant, and a widely published author

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